1. Field of the Invention
The present invention relates to methods of processing an orientation film to orient liquid crystal molecules thereon for use in a liquid crystal display panel.
2. Background Art
One conventional method of orienting liquid crystal molecules for use in a liquid crystal display panel is to rub a surface of an orientation film, provided on a surface of a substrate which composes a part of the liquid crystal display panel, with a rubbing roll in one direction. When a film substrate is used as the substrate, rubbing film substrates having a given length corresponding to respective liquid crystal display panels is inefficient. Thus, a long film substrate from which many substrates for many liquid crystal display panels can be made at a time is rubbed in a tensile state between roll units.
FIG. 4 shows a part of a conventional orientation device used in such orientation process, in which an elongate film lamination 1 is conveyed intermittently in the direction of an arrow A along an upper surface of a stage 2. The film lamination 1 is composed of a film substrate, a transparent electrode of ITO (Indium Tin Oxide) or the like (not shown) formed on an upper surface of the substrate, and an orientation film of a resin such as polyimide formed on an upper surface of the electrode (not shown). A rubbing roll 3 is disposed above the stage 2. The roll 3 is made of a roll core and a nappy cloth wound around the roll core. The roll 3 is rotatable in a horizontal plane around the midpoint of its length in order to set a rubbing angle thereof, movable vertically, movable in the direction of arrow C while rotating in the direction of arrow B and movable in the direction opposite to the direction of arrow C.
When the film lamination 1 which is conveyed intermittently in the direction of arrow A stops, the rubbing roll 3 the rubbing angle of which is set moves from the down position shown by the solid line in FIG. 4 in the direction of arrow C to come into contact with a surface of the orientation film in a predetermined range on the film lamination 1. At this time, the rubbing roll 3 rotates in the direction of arrow B opposite to the direction of arrow C to thereby rub the surface of the orientation film of the film lamination 1 in the predetermined range in one direction. Thereafter, the roll 3 arrives at the position shown by the two-dot chain line in FIG. 4, rises, moves in the direction opposite to the direction of arrow C, arrives at the position shown by the solid line in FIG. 4 and then lowers. During the movement of the roll 3 in the direction opposite to the direction of arrow C, the film lamination 1 is conveyed by a predetermined distance in the direction of A.
Since the film lamination 1 is rubbed when it is at a stop in the conventional orienting method, however, conveyance of the film lamination 1 is stopped each time rubbing is performed. Thus, the problem is that productivity is low.
Since the film lamination 1 is conveyed intermittently, and if the accuracy of the stopping position of the film lamination 1 is low, the trailing end of the orientation film in a rubbing range and the leading end of the orientation film in the next rubbing range would overlap, so that a doubly rubbed area of the film lamination would result or no rubbed area would result. Thus, the stopping position of the film lamination 1 is required to have a high accuracy.
Unless the upper surface of the stage 2 is parallel to the plane of movement of the rubbing roll 3, uneven rubbing would result. Thus, high accuracy of parallelism is required between the upper surface of the stage 2 and the plane of movement of the rubbing roll 3.